During a conference, at least two communication systems (i.e., a near-end unit and a far-end unit) participate in a call. Typically, the units will have near-end echo cancellation. For example, a near-end unit 10 schematically shown in FIG. 1 has an audio decoder 12, an audio coder 14, a loudspeaker 20, and a microphone 40 and communicatively couples to a far end unit 16 using techniques known in the art. During a conference, the audio decoder 12 receives far-end audio, decodes it, and sends the decoded audio to the loudspeaker 20 so the near-end participant can listen. In turn, the microphone 40 picks up near-end audio from the participant, and the audio coder 14 encodes the near-end audio and sends it to the far-end unit 16. Due to the proximity of the loudspeaker 20 and microphone 40, acoustic coupling (indicated by arrow 11) may occur in which far-end audio output by the loudspeaker 20 is picked up by the microphone 40 and fed back to the far-end unit 16.
To reduce the effects of this acoustic coupling (11), the near-end unit 10 has a near-end echo canceller 30 that operates between the decoder/coder 12/14 and the loudspeaker/microphone 20/40. The near-end echo canceller 30 subtracts the audio emitted from the loudspeaker 20 that has been picked up by the microphone 40. The audio coder 14 then transmits the resulting signal to the far-end unit 16. In this way, the near-end echo cancellation reduces the acoustic coupling in the loudspeaker-to-microphone acoustic path at the near-end and helps to prevent the far-end participant from hearing his own voice come back to him as returned echo.
Although near-end echo cancellation may be used at the near-end unit, the far-end unit 16 in some instances may not have a working acoustic echo canceller. In this case, the near-end participant will hear his voice come back to him due to the acoustic coupling (indicated by arrow 17) between the loudspeaker and microphone at the far-end. Therefore, near-end echo cancellation may benefit the person at the far-end, but it does nothing to prevent the near-end from hearing near-end audio returned from the far-end as echo.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.